In maintaining the aesthetic appearance of a floor, it is common practice to coat the floor with a lustering agent, thereby protecting the floor. Lustering agents consisting mainly of wax which are defined in the Japanese Industrial Standards “JIS K3920”, such as an oily floor polish, an emulsifiable floor polish, and a wax type aqueous floor polish, were predominant in the past. However, such wax-based lustering agents were disadvantageous, for example, because they required polishing work after coating, and they were inferior in aspects of durability such as persistence of gloss and the degree of dirt adhesion.
To deal with these disadvantages, Patent Documents 1, 2 and Non-Patent Document 1, for example, have proposed emulsions of metal-crosslinked acrylic copolymers, polyethylene wax emulsions, and polymer type aqueous floor polishes comprising alkali-soluble resins and plasticizers (hereinafter referred to as “resin waxes”).
With such resin waxes, polishing work after coating is unnecessary, and the aspects of durability such as persistence of gloss and the degree of dirt adhesion can be improved in comparison with the above wax-based lustering agents. With the passage of time, however, gloss declines, and dirt and black heel marks (black marks of a shoe sole shaved off) become conspicuous.
With a coating of the resin wax, therefore, if its deterioration is marked, it has been necessary to swell the coating with a solvent component, and cut the metal-crosslinked portion of the acrylic resin into pieces by an alkali component, with the use of a release agent comprising a glycol-based solvent or a glycol ether-based solvent, a chelating agent, an amine, an inorganic alkali, a wetting agent, etc., remove all the pieces from the floor surface by use of a polisher, and then newly coat the resin wax, thereby repairing the floor coating.
Such repair work requires a lot of time. If the coating film deposited is thick, in particular, it has been difficult to remove the coating film completely at a time, and a plurality of repair operations have been required. Moreover, a waste liquor of the used release agent has so high values of BOD, COD, n-hexane extracts, and total nitrogen that the waste liquor cannot be discarded as such. The waste liquor needs to be post-treated in order to lighten burden on the environment. Thus, very complicated operations have been needed, and costs have been burdensome.
In recent years, proposals have been made for silicone-based inorganic coating agents as described in Patent Document 3, etc., and ultraviolet curable coating agents as described in Patent Document 4, etc., which have even higher durability while further suppressing tiny scars or dirt. Such coating agents, however, have posed problems such that deep scars enter the resulting coating over time, making repair difficult, and that stripping work cannot be done easily. Thus, the widespread use of the coating agents has not been made.
Patent Document 5, for example, proposes a strippable coating composition for floors which can form a film-like coating on a floor surface. With such a strippable coating composition for floors, the coating can be peeled off the floor surface as a single film. Thus, it can be easily removed without the use of a release agent, and the efficiency of removal work can be increased.
The strippable coating composition for floors described in Patent Document 5, etc., however, is of a two-part coating type which involves coating of a liquid for forming a strippable layer exhibiting peel performance relative to the floor surface, followed by coating of a liquid for forming a stain-proof layer for preventing dirt, stain or the like. Thus, the strippable coating composition for floors has posed the problem of requiring much time and labor for its application.
To solve the problem of the above two-part coating type, Patent Document 6 to be indicated below proposes a one-part coating type strippable coating composition for floors which has a material dispersed in water, the material adapted to form a coating film essentially consisting of a urethane resin with specified film properties such as break strength and elongation at break.
However, the above-mentioned one-part coating type coating composition tends to be poor in drying characteristics or dryness. Furthermore, the coating composition has involved the following problems: When an end of the coating film applied to the floor surface is turned up with a cutter or the like and peeled, the film may be trapped, for example, by a scar in the floor surface or the joint of the tile, and tear may occur. In this case, the tear caused to the coating film may spread in the stripping direction, so that the coating film becomes difficult to peel as a single continuous film. As a result, an end of the coating film remaining intact on the floor surface has to be turned up again using a cutter or the like, and peeled anew. Thus, the stripping work efficiency lowers.
To solve the above problems, Patent Document 7 to be indicated below proposes a coating composition providing a film for which tearing force is further specified. This coating composition has been improved in decreased work efficiency, but has still been unsatisfactory in the property of preventing dirt adhesion or anti-dirt adhesion (black heel mark resistance) as well as in water resistance.